64 



PERMO-CARBONIFEROUS VERTEBRATES FROM NEW MEXICO. 



the scapula and coracoid (metacoracoid Williston) and procoracoid (coracoid Willis- 

 ton) are distinct, and the posterior bone is easily separable — there are two isolated 

 posterior coracoid bones in the collection. The anterior border of the bone is 

 destroyed in both specimens, so that it is impossible to determine the presence or 

 absence of facets for the attachment of a clavicle or cleithrum. The proximal end 

 carries a large preglenoid tuberosity, with an articular glenoid face looking back- 

 ward and downward. There is no foramen on the posterior face of the preglenoid 

 tuberosity, such as occurs in Dimetrodon. Below the posterior part of the edge of 

 the tuberosity there is an indication of a glenoid foramen, and below the anterior 

 part of the same border is the usual supracoracoid foramen. Both foramina open 

 into a subscapular fossa on the inner side of the bone, as in Dimetrodon. The poster.or 

 of the two coracoid bones has the same form as in Dimetrodon. The glenoid face looks 



Fig. 40. — Sphenacodon ferox Marsh, X K- A, right scapula; B, left clavicle; C, fragment of left 

 side of pelvis; D, left side of axis; E, anterior view of axis. 



forward, upward, and outward, completing the glenoid cavity identical in form and 

 position with that of Dimetrodon and Ophiacodon. The anterior coracoid bone, the 

 procoracoid of authors, is complete in one specimen, but the scapula is broken 

 away along the line of iinion between the two (fig. 40 a). This edge is perfect, 

 extending almost directly outward from the lower part of the scapula. As a whole, 

 the proximal margin formed by the two coracoid bones is nearly straight, except 

 at the front end. 



Clavicles (fig. 40 b) : Associated with the skull are two clavicles. That of the 

 right side is more perfect than that of the left; its proximal end is wide and flat, 

 and evidently articulated with the interclavicle, as in Dimetrodon. The distal end 

 is narrower, and there is a deep groove on the lower edge which received the border 

 of the scapula. The anterior border is deeply concave longitudinally. The whole 

 bone is different from that of Dimetrodon; in that genus the proximal end is wider 

 and the distal end narrower, without a groove on the lower edge for the scapula. 



